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-rw-r--r--src/osmo-bts-trx/gsm0503_interleaving.c144
1 files changed, 144 insertions, 0 deletions
diff --git a/src/osmo-bts-trx/gsm0503_interleaving.c b/src/osmo-bts-trx/gsm0503_interleaving.c
new file mode 100644
index 00000000..ec47a6b3
--- /dev/null
+++ b/src/osmo-bts-trx/gsm0503_interleaving.c
@@ -0,0 +1,144 @@
+
+#include <stdint.h>
+
+#include <osmocom/core/bits.h>
+
+#include "gsm0503_tables.h"
+#include "gsm0503_interleaving.h"
+
+/*
+ * GSM xCCH interleaving and burst mapping
+ *
+ * Interleaving:
+ *
+ * Given 456 coded input bits, form 4 blocks of 114 bits:
+ *
+ * i(B, j) = c(n, k) k = 0, ..., 455
+ * n = 0, ..., N, N + 1, ...
+ * B = B_0 + 4n + (k mod 4)
+ * j = 2(49k mod 57) + ((k mod 8) div 4)
+ *
+ * Mapping on Burst:
+ *
+ * e(B, j) = i(B, j)
+ * e(B, 59 + j) = i(B, 57 + j) j = 0, ..., 56
+ * e(B, 57) = h_l(B)
+ * e(B, 58) = h_n(B)
+ *
+ * Where hl(B) and hn(B) are bits in burst B indicating flags.
+ */
+
+void gsm0503_xcch_deinterleave(sbit_t *cB, sbit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<456; k++) {
+ B = k & 3;
+ j = 2 * ((49 * k) % 57) + ((k & 7) >> 2);
+ cB[k] = iB[B * 114 + j];
+ }
+}
+
+void gsm0503_xcch_interleave(ubit_t *cB, ubit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<456; k++) {
+ B = k & 3;
+ j = 2 * ((49 * k) % 57) + ((k & 7) >> 2);
+ iB[B * 114 + j] = cB[k];
+ }
+}
+
+/*
+ * GSM TCH FR/EFR/AFS interleaving and burst mapping
+ *
+ * Interleaving:
+ *
+ * Given 456 coded input bits, form 8 blocks of 114 bits,
+ * where even bits of the first 4 blocks and odd bits of the last 4 blocks
+ * are used:
+ *
+ * i(B, j) = c(n, k) k = 0, ..., 455
+ * n = 0, ..., N, N + 1, ...
+ * B = B_0 + 4n + (k mod 8)
+ * j = 2(49k mod 57) + ((k mod 8) div 4)
+ *
+ * Mapping on Burst:
+ *
+ * e(B, j) = i(B, j)
+ * e(B, 59 + j) = i(B, 57 + j) j = 0, ..., 56
+ * e(B, 57) = h_l(B)
+ * e(B, 58) = h_n(B)
+ *
+ * Where hl(B) and hn(B) are bits in burst B indicating flags.
+ */
+
+void gsm0503_tch_fr_deinterleave(sbit_t *cB, sbit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<456; k++) {
+ B = k & 7;
+ j = 2 * ((49 * k) % 57) + ((k & 7) >> 2);
+ cB[k] = iB[B * 114 + j];
+ }
+}
+
+void gsm0503_tch_fr_interleave(ubit_t *cB, ubit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<456; k++) {
+ B = k & 7;
+ j = 2 * ((49 * k) % 57) + ((k & 7) >> 2);
+ iB[B * 114 + j] = cB[k];
+ }
+}
+
+/*
+ * GSM TCH HR/AHS interleaving and burst mapping
+ *
+ * Interleaving:
+ *
+ * Given 288 coded input bits, form 4 blocks of 114 bits,
+ * where even bits of the first 2 blocks and odd bits of the last 2 blocks
+ * are used:
+ *
+ * i(B, j) = c(n, k) k = 0, ..., 227
+ * n = 0, ..., N, N + 1, ...
+ * B = B_0 + 2n + b
+ * j, b = table[k];
+ *
+ * Mapping on Burst:
+ *
+ * e(B, j) = i(B, j)
+ * e(B, 59 + j) = i(B, 57 + j) j = 0, ..., 56
+ * e(B, 57) = h_l(B)
+ * e(B, 58) = h_n(B)
+ *
+ * Where hl(B) and hn(B) are bits in burst B indicating flags.
+ */
+
+void gsm0503_tch_hr_deinterleave(sbit_t *cB, sbit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<228; k++) {
+ B = gsm0503_tch_hr_interleaving[k][1];
+ j = gsm0503_tch_hr_interleaving[k][0];
+ cB[k] = iB[B * 114 + j];
+ }
+}
+
+void gsm0503_tch_hr_interleave(ubit_t *cB, ubit_t *iB)
+{
+ int j, k, B;
+
+ for (k=0; k<228; k++) {
+ B = gsm0503_tch_hr_interleaving[k][1];
+ j = gsm0503_tch_hr_interleaving[k][0];
+ iB[B * 114 + j] = cB[k];
+ }
+}
+